It is known to enclose fluid substances (both liquid and creamy) in containers from which these substances are dispensed by manually operating a small pump mounted on the mouth of a respective container. to Pump operation causes a quantity of fluid substance to be withdrawn from the container in which—if the container is rigid—a vacuum forms which would prevent further substance withdrawal and dispensing if air were not allowed to enter the container (which generally takes place in those regions in which the pump makes contact with and slides on the pump body), or if the container did not comprise a base sealedly movable along an internal cylindrical surface of the container (see for example U.S. Pat. Nos. 4,691,847, 4,694,977 and 5,971,224): this latter system for compensating the container volume by reducing its internal volume while maintaining the internal pressure constant is however very laborious and costly.
In many cases it is opportune or necessary that the fluid substance to be dispensed by a pump never comes into contact with the atmosphere inside the container (with the dispensing pump mounted on it): sealing the fluid out of contact with the atmosphere is important if the composition of the fluid within the container is not to undergo alteration, or if it is essential that the fluid substance enclosed in the container remains sterile. To achieve this, U.S. Pat. No. 3,420,413 has proposed a device comprising a bag containing the fluid substance which is to remain isolated (from the atmosphere) inside the bag which (see column 4, lines 22-28) is made of elastically deformable flexible material and has a neck on which a support element (having a profiled aperture for housing a pump) is sealedly applied after the bag has been filled with the fluid substance to be dispensed: after this, a pump is sealedly mounted on said support element to hence prevent contamination of the fluid substance by the air (column 5, lines 15-38). The bag containing the fluid substance and having the pump sealedly mounted on its neck is then inserted into a rigid body (obviously being very careful that the free end of the rigid body does not come into contact with the bag filled with fluid substance, in order not to break it) on which said support element is then positioned and fixed (column 5, lines 56-61). Hence between the outer surface of the bag and the inner surface of the rigid body an interspace is formed which is connected to atmosphere via a hole provided in the container base; in this manner, when the fluid substance is withdrawn from the bag by operating the pump, the bag is squeezed by the atmospheric pressure so that the substance can be easily withdrawn and expelled to the outside by the pump (column 5, lines 70-73). The main drawback of the aforesaid device is that the deformable bag must be filled with fluid substance before the bag is inserted into the respective rigid container and that the operation involved in inserting the bag into the container is very delicate because the bag can be easily torn while being inserted into the container interior.
JP 05 031790A and JP 05 031791A published on Sep. 2, 1993 describe how a bag of elastically deformable material can be produced directly within a rigid container. For this purpose an elongated preform (made of thermoplastic material and having an elongated hollow cylindrical body, open at one end where the preform presents a neck from which a flange radially projects) is inserted into a rigid container having a mouth from which a neck extends, on the free edge of which there rests the flange of the preform, which is heated, thrust towards the container base by a pusher and then inflated within the container, until a bag forms, the outer surface of which adheres (at least for a large part of its surface) to the inner surface of the container. The bag obtained in this manner also has a neck, at least an end portion of which presents outwardly projecting longitudinal ribs, with some radial ribs or projections projecting from that surface of the preform flange which faces the free edge of the neck of the container in which the bag is inserted: these ribs or projections define passages for the air which penetrates from the outside between the container and bag to enable this latter to flatten or inwardly deform during outward dispensing of the fluid substance through the pump, so preventing the formation inside the bag of a vacuum which would prevent dispensing of the fluid substance.
In particular, in the two Japanese patents the method used to inflate the bag within the container imposes considerable stresses on the bag which can break it both during inflation and during use.
This is substantially due both due to the fact that the production method causes the bag to adhere at least in some points to that part of the cavity within which it is inflated, and to the fact that the initial stretching caused by the pusher creates non-uniformity in the final thickness of the bag walls which are thinner in the top lateral region than in proximity to the base and in the base itself.
A further problem of the known art is that by inflating the bag by the aforedescribed system it is not possible to completely fill the cavity. In other words, container regions remain in which the bag is very detached from the wall defining the cavity. This occurs not only in those positions “difficult” to fill by inflation, for example close to corners, but also in regions pertaining or close to the container walls. This is due to the presence of air pockets which remain trapped within the interspace between the bag and cavity during inflation.